5310-00-285-2181 (630004)
NSN 5310-00-285-2181 (NIIN 00-285-2181) is a hexagon plain nut in Federal Supply Class 5310, Nuts And Washers — a nut, flat on top and bottom having 6 flat sides. Manufacturer part number 630004 (Am General LLC, CAGE 34623); also referenced as 8332520 (U S Army Tank Automotive Command).
NIIN assigned January 1963; DEMIL A (none required).